1. Field of the Invention
The present invention relates to a polysiloxane composition and a rubber composition containing a surface-treated inorganic solid particle treated, on the surface thereof, with the same well as a resin composition containing a resin, an inorganic filler and a polysiloxane suitable for use as a paint, adhesive, sealant, etc. due to a superior stability of dispersion of a filler.
2. Description of the Related Art
In the past, inorganic solid particles such as carbon black, calcium carbonate, alumina, aluminum sulfate, barium sulfate, calcium sulfate, silica, talc, clay, diatomaceous earth, and mica have been used in numerous fields such as rubber, cosmetics, synthetic resins, paints, adhesives, and magnetic tape. Among these, inorganic solid particles are extensively used as fillers for various types of rubber. These inorganic solid particles sometimes have polar groups on their surface. The inclusion of inorganic solid particles is problematic in that it causes a drop in the knit of the mix with the rubber. Rubber compositions containing metal oxides containing silica, in particular silica, among these inorganic solid particles are used for tire tread rubber compositions low in heat buildup and superior in abrasion resistance. Rubber compositions containing silica are problematic in that the viscosity at the time before vulcanization rises, the vulcanization is delayed, and the knit of the mix falls and the productivity consequently deteriorates. Further, in a rubber composition containing silica, poor dispersion of the silica occurs and the properties of the silica are not sufficiently utilized.
To solve the above problem, the present inventors previously found that the unvulcanized physical properties and vulcanized physical properties of the rubber composition containing silica can be improved by blending an alkoxysilyl group-containing polysiloxane in a rubber composition containing silica, whereby a reaction between the silanol groups on the surface of the silica and alkoxysilyl groups is caused to thereby cover the surface of the silica (see Japanese Unexamined Patent Publication (Kokai) No. 9-111044). However, it was found that, when the polysiloxane is stored for a long period, an increase in the viscosity is seen and the improvement in the unvulcanized physical properties and vulcanized physical properties in a rubber composition containing silica using such a polysiloxane is small.
In addition, resin compositions for paints, adhesives, sealants, etc. use pigments and other fillers for coloring, blocking, reinforcement, extension, imparting weather resistance, or imparting conductivity, a magnetic property, or other properties. Fillers are classified into inorganic fillers and organic fillers, but the former is generally low in affinity with various resins, and therefore, poor dispersion, aggregation, settling, etc. easily occur and, in turn, painting or installation become impossible, uneven coloring, blocking, etc. occur, and other problems arise.
Among the inorganic fillers, silica is used in paints as an extender pigment or delustering agent and is used in adhesives for improvement of the hardness etc., but due to the aggregating force arising from the silanol groups on the surface, poor dispersion and settling in particular easily occur or, once precipitating, redispersion is extremely difficult.
To solve this problem, various dispersants and anti-settling agents for use for paints, adhesives, sealants, and other resin compositions have been studied in the past.
For example, Japanese Unexamined Patent Publication (Kokai) No. 5-163463 describes that a "condensate of an organoalkoxysiloxane having the general formula: EQU RSi(OR').sub.3
where R represents a C.sub.1 to C.sub.8 organic group and R' represents a C.sub.1 to C.sub.5 alkyl group or C.sub.1 to C.sub.4 acyl group, i.e. an organosiloxane having a weight average molecular weight converted to polystyrene of 3,000 to 100,000" improves the dispersion of the pigment and acts as a condensing agent in a coating composition.
However, in the above system, dual use of colloidal silica is essential. Further, the publication does not describe anything about the effect of an organopolysiloxane as a dispersant and anti-settling agent in a coating composition where the pigment is silica and does not solve the problem of poor dispersion, aggregation, settling, and difficult redispersion of silica.